Are you not aware that the LA-area cops have already shot up two different vehicles in one day, in incidents in which the people in the vehicles were completely innocent, and no guns and no fireworks were involved?
Maybe you're not following the news. These cops are on a hair trigger, and they are heavily armed and pretty much prepared to shoot down even innocent civilians. I think your suggestion that someone might set off fireworks into that powder keg might be something you might want to think a bit more about.
Okay, I retract my statments.